Transmission of malaria from masquitoes to humans appears deceptively simple. Although the role of the mosquito in this complex life cycle has been known for more than 100 years, the factors which govern the differentiation of initially asexual parasites to gametocytes remains unknown. This project draws upon recent molecular advances which define the point at which parasites commit to sexual development, and has utilized that information to search for the relevant genes in this process. The next steps in this process involve a mix of field studies and molecular laboratory work, as well as molecular studies in the field. Using this approach it is likely that these studies will substantially enhance our understanding of the transmission of malaria. From a more practical perspective this information should be valuable for the design and evaluation of vector control strategies as diverse as insecticide treated bednets and potential transmission blocking vaccines. Finally, the studies proposed here bring together two highly committed groups in entomology working from different perspectives towards a common goal of disease control.